References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-6-5537-2006

Reflection and transmission of solar light by clouds: asymptotic theory

Kokhanovsky

A. A.

¹ Nauss

Institute of Remote Sensing, University of Bremen, O. Hahn Allee 1, 28334 Bremen, Germany

Laboratory of Climatology and Remote Sensing, Marburg University, Deutschhausstr. 10, 35032 Marburg, Germany

11 12 2006

6 12 5537 5545

This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

This article is available from http://www.atmos-chem-phys.net/6/5537/2006/acp-6-5537-2006.html

The full text article is available as a PDF file from http://www.atmos-chem-phys.net/6/5537/2006/acp-6-5537-2006.pdf

The authors introduce a radiative transfer model CLOUD for reflection, transmission, and absorption characteristics of terrestrial clouds and discuss the accuracy of the approximations used within the model. A Fortran implementation of CLOUD is available for download. This model is fast, accurate, and capable of calculating multiple radiative characteristics of cloudy media including the spherical and plane albedo, reflection and transmission functions, absorptance as well as global and diffuse transmittance. The approximations are based on the asymptotic solutions of the radiative transfer equations valid at cloud optical thicknesses larger than 5. While the analytic part of the solutions is treated in the code in an approximate way, the correspondent reflection function (RF) of a semi-infinite water cloud R∞ is calculated using numerical solutions of the radiative transfer equation in the assumption of Deirmendjian's cloud C1 model. In the case of ice clouds, the fractal ice crystal model is used. The resulting values of R∞ with respect to the viewing geometry are stored in a look-up table (LUT). The results obtained are of importance for quick estimations of main radiative characteristics of clouds and also for the solution of inverse problems.

References 1

King, M. and Harshvardhan: Comparative accuracy of selected multiple scattering approximations, J. Atmos. Sci., 44, 1734–1751, 1986.

Kokhanovsky, A. A., Rozanov, V. V., Zege, E. P., Bovensmann, H., and Burrows, J. P.: A semi-analytical cloud retrieval algorithm using backscattered radiation in 0.4–2.4 μm spectral region, J. Geophys. Res., 108, 4008, doi:10.1029/2001JD001543, 2003.

Kokhanovsky, A. A.: Cloud Optics, Berlin: Springer-Verlag, 2006.

Mishchenko, M. I., Dlugach, J. M., Yanovitskij, E. G., and Zakharova, N. T.: Bidirectional reflectance of flat, optically thick particulate layers: an efficient radiative transfer solution and applications to snow and soil surfaces, J. Quant. Spectrosc. Radiat. Trans., 63, 409–432, 1999.

Nakajima, T. and King, M. D.: Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements, Part 1. Theory, J. Atmos. Sci., 47, 1878–1893, 1990.

Rozanov, A. V., Rozanov, V., Buchwitz, M., Kokhanovsky, A., and Burrows, J. P.: SCIATRAN 2.0: a new radiative transfer model for geophysical applications in the 175–2400 nm spectral region, Adv. in Space Res., 36, 1015–1019, 2005.

van de Hulst, H. C.: The spherical albedo of a planet covered with a homogeneous cloud layer, Astron. Astrophys., 35, 209–214, 1974.

van de Hulst, H. C.: Multiple Light Scattering: Tables, Formulas and Applications, N.Y., Academic Press, 1980.

Wauben, W. M. F.: Multiple Scattering of Polarized Radiation in Planetary Atmospheres, Ph.D. Thesis, Free University of Amsterdam, 1992.